Psychophysical thresholds will be measured in quantitative studies of binocular interaction in human pattern vision. Half fields of a split-screen visual display will be presented dichoptically to the two eyes of observers. The stimulus patterns will be sinewave gratings, characterized by their spatial frequency, relative phase, contrast, orientation, and temporal waveform. There are three broad research objectives: 1) to undestand how stereopsis is influenced by pattern parameters of the two half fields; 2) to understand how monocular contrast thresholds depend upon parameters of the stimulus presented to the contralateral eye; 3) to develop a general psychophysical procedure for the characterization of nonlinear perceptual systems. These objectives will be pursued in seven experiments concerned with: 1) the influence of the binocular accommodation response on contrast thresholds; 2) interocular "summation" of temporal, spatial and orientational parameters of the masking stimulus, as well as its stereoscopic disparity; 4) dependence of stereoscopic and vernier acuity and discrimination thresholds upon spatial frequency, contrast and orientation.